在Dartlang中实现链表上的Iterable类？

class Node<T> {
  T value;
  Node<T> next;

  Node(this.value, [this.next]);
}

class LinkedList<T> {
  Node<T> head;

  void add(T value) {
    if (head == null) {
      head = Node(value);
    } else {
      Node<T> current = head;
      while (current.next != null) {
        current = current.next;
      }
      current.next = Node(value);
    }
  }

  void remove(T value) {
    if (head == null) {
      return;
    }
    if (head.value == value) {
      head = head.next;
      return;
    }
    Node<T> current = head;
    while (current.next != null) {
      if (current.next.value == value) {
        current.next = current.next.next;
        return;
      }
      current = current.next;
    }
  }
}

class LinkedList<T> implements Iterable<T> {
  // ...

  @override
  Iterator<T> get iterator => LinkedListIterator<T>(head);
}

class LinkedListIterator<T> extends Iterator<T> {
  Node<T> _current;

  LinkedListIterator(this._current);

  @override
  T get current => _current?.value;

  @override
  bool moveNext() {
    if (_current == null) {
      return false;
    }
    _current = _current.next;
    return _current != null;
  }
}

void main() {
  LinkedList<int> list = LinkedList<int>();
  list.add(1);
  list.add(2);
  list.add(3);

  for (int value in list) {
    print(value);
  }
}

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